The invention relates to a load-shifting device for a motor vehicle, the device having a requlating element which can act on a setting member which determines the output of an internal combustion engine, and wherein the regulating element is connected to a driver which is coupled with an accelerator pedal. The regulating element can be moved by means of an electric setting drive, there being a desired-value detection element associated with the driver and an actual-value detection element cooperating with the driver and acting on the electric setting drive, the electric setting drive being regulatable as a function of the values of vehicle and engine speed applied to an electronic control device.
Load-shifting devices of this type are provided in motor vehicles for actuating the throttle valve or the injection pump by the accelerator pedal in order, by means of the electronic regulating device, to be able to intervene in such a manner that, for instance, wheel spinning upon starting as a result of too high a power is avoided. The regulating device provides that, in the event of too rapid a depression of the accelerator pedal, that, for instance, the throttle is opened less than corresponds to the position of the accelerator pedal so that the internal combustion enqine produces merely a power which does not lead to any spinning of the wheels. Other automatic interventions in the load-shifting device are necessary if a transmission is to be switched automatically or if the idling speed of rotation is to be set to a constant value upon idling, even in the event of different power requirements. It is desirable in such a shifting device to intervene by a speed-limiting controller which, by the possibility of uncoupling the control element from the accelerator pedal, provides in each case that power is set which is necessary in order to maintain the speed which has been set. In addition, it may be desirable, in particular from the standpoint of comfort in driving, to provide for a progressive or degressive connection of the accelerator pedal, with the possibility of a power setting which is reduced or increased as compared with the position of the accelerator pedal.
Safety factors, however, make it necessary that, in the event of a defect in the control device, assurance is had that upon a reduction of the position of the accelerator pedal the power setting decreases synchronously with the position of the accelerator pedal. Up to now, this has been achieved by safety devices in the electronic control device. Possibilities of error in the control device are reduced in the manner that the electronics are provided redundantly. Nevertheless, too high a power setting which does not correspond to the position of the accelerator pedal is not completely excluded in the event of a defect.
It is an object of the invention so to develop a load-shifting device of said type in such a manner that the functionability of the electronic regulation of the setting member via the gas pedal and thus the functionability of the electronic control device is continuously monitored and, even in the event of a failure of the electronic control device, a specifically defined reaction on the setting member and consequently on the throttle valve or injection pump is possible.